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    <title>Document</title>
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    <script>
        let arr = [2, 6, 1, 7, 4]
        // 1.求和的变量sum
        let sum = 0
        // 2. 遍历累加
        for (let i = 0; i < arr.length; i++) {
            sum += arr[i]
        }
        console.log(`arr的和是:${sum}`);
        // 3. 平均值 sum/arr.length
        console.log(`arr的平均值是:${sum / arr.length}`);
    </script>
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